Generally, air conditioning (A/C) apparatuses for cooling or heating passenger compartments are installed in vehicles. Such an air conditioning apparatus includes, as a configuration for a cooling system, a compressor, which compresses low-temperature and low-pressure gaseous refrigerant drawn from an evaporator into a high-temperature and high-pressure gaseous state, and transfers it to a condenser.
Compressors are classified into a reciprocating compressor which compresses refrigerant using reciprocating motion of a piston, and a rotary compressor which performs rotational motion to compress refrigerant. According to a drive force transmission method, reciprocating compressors are classified into a crank type in which drive force is transmitted by a plurality of piston using a crank, a swash plate type in which drive force is transmitted by a rotating shaft provided with a swash plate, and so forth. Rotary compressors are classified into a vane rotary type which employs a rotary shaft and vane, and a scroll type which employs a turning scroll and a fixed scroll.
In compressors, as a compression unit is driven by rotating a rotor, refrigerant is compressed. In this regard, since movable parts of the compression unit including a rotating part such as the rotor repeatedly make friction with stationary parts, lubrication is necessarily required. Particularly, in the case of the scroll compressor, lubrication between the fixed scroll and the turning scroll is very important. To minimize power loss and prevent damage due to abrasion, friction between the fixed scroll and the turning scroll must be minimized, but to enhance compression efficiency, leakage of refrigerant between the fixed scroll and the turning scroll must also be minimized.
For this, hitherto, a method in which oil is mixed with refrigerant to lubricate mechanical friction portions in a compression chamber has been used. This method is efficient because an oil supply structure can be simplified, but is problematic in that some oil mixed with refrigerant is discharged out of the compressor and thus the amount of oil is reduced.
To overcome the foregoing problem, an oil separator is used along with the compressor. For a certain shape, the oil separator may be separately provided from the compressor. However, in the case of, e.g., a vehicle which cannot provide sufficient installation space, the oil separator may be integrally formed in a compressor housing. Typically, such an oil separator collects oil from refrigerant while colliding with the refrigerant discharged out of the compressor, and returns the collected oil to the compressor. When oil returned in this way is supplied into the compressor, oil must be supplied at an appropriate flow rate to desired parts of the compressor. However, due to this, there is a problem in that an oil supply passage is complex. Therefore, a method capable of efficiently supplying returned oil despite having a simple oil supply passage is required.